Circuit breaker



May l0, 1938. J. G. JACKSON 2,116,791

C IRCUIT BREAKER .5 f5 @i @E 2:1212

INVENTOR. Jahr? 6'. L/'aclon 725m fa-Ma ATTORNEY.

May 10, 1938. J. G. JACKSON 2,116,791

CIRCUIT BREAKER lill,

INVENTOR.

/30 Lfo/zfz 6.

/94 L5 By J t /-9/ /32 @H '1 E' ATTORNEY,

Patented May 10, 1938 UNITED STATES PATENT OFFICE cnwurr nimma tion ofMichigan Application December 27, 1934, Serial No. 759,353

21 Claims.

This invention relates generally to apparatus for making and breaking anelectrical circuit and more particularly to circuit breakers havingcurrent responsive devices which operate to automatically break thecircuit in response to predetermined current values.

One vobject of this invention is to provide a. circuit breaker having animproved construction for producing both quick make and quick breakcontact operation.

Another object of this invention is to provide a circuit breaker whichis to be automatically tripped by the action oi a thermostatic memberinfluenced by the current passing therethrough in which a shunt isprovided for the thermostatic member to by-pass a portion of the currentthere-around.

Another object of this invention is to provide a circuit breaker whichis to be automatically tripped by the action of a thermostatic memberinuenced by the current passing therethrough in which a shunt isprovided for the thermostatic member to by-pass a portion of the currenttherearound, the resistance of the shunt being adjustable to permit thesame thermostatic member to be utilized to interrupt the circuit atdifferent predetermined values of circuit current.

Another object of this invention is to provide a circuit breaker whichis to be automatically tripped by the action of a thermostatic memberinfluenced by the current passing therethrough in which a shunt isprovided for the thermostatic member to by-pass a portion of the currenttherearound, the resistance of the shunt being adjustable to permit thesame thermostatic member to be utilized to interrupt the circuit atdifferent predeterminedvalues of circuit current and in which the shuntis arranged to limit the maximum value of current below which thecircuit 40 breaker will not respond to a safe value.

A further object of the invention is to provide an arc suppressor whichwill operate efliciently over a wide range of current values.

A still further object of the invention is to pro- 45 vide a scalablecircuit breaker having an improved interlock between the cover and theoperating handle to prevent removal of the cover while the circuitbreaker is in the on position.

Another object of the invention is to provide a 50 circuit breaker inwhich the contacts cannot be engaged by movement of the operating handlewhile the cover is removed.

A still further object of the invention is to provide a circuit breakerin which the initial force on the contact arm when the operating handleis moved toward on position is in a direction to further separate thecontact members.

Further objects and features of the invention will be readily apparentto those skilled in the art from the following specification and the ap-5 pended drawings illustrating certain preferred embodiments of theinvention in which:

lFigure 1 is a vertical longitudinal sectional view showing one form ofthe improved circuit breaker in oi position.

Figure 2 is a view similar to Figure 1 with contacts engaged.

Figure 3 is a broken sectional view similar to Figure 1 showing theparts in initially tripped position.

Figure 4 is a sectional view taken on the lines IV--IV of Figure 2. v

Figure 5 is a sectional view taken on the lines V-V of Figure 1.

Figure 6 is a sectional yview taken on the line VI-VI of Figure 2.

Figure 7 is a sectional view taken on the line VII--VII of Figure 2.

Figure 8 is a vertical longitudinal sectional view of a circuit breakerillustrating another form of the invention with the parts in normal 01Tposition.

Figure 9 is a sectional view similar to Figure 8 showing the parts withthe contacts in engaged position, the automatic trip position of certainof the parts, and a removal position of the cover, being shown in dottedlines.

' Figure 10 is a sectional view taken on the line X-X of Figure 9.

Figure 11 is a sectional view taken on the line XI--XI of Figure 8.

Figure 12 is a vertical longitudinal sectional view through a modifiedform of arc suppressor.

Figure 13 is a sectional View taken on the line XIII-XIII of Figure 12,and

Figure 14 is a vertical longitudinal sectional view through a stillfurther modiilcation of the arc suppressor.

Referring now particularly to the device as illustrated in Figures 1 to7 inclusive, the circuit breaker as shown comprises a box like bodyportion I having an open bottom 2 closed by plate 3. In the top of thebody portion is provided a slot 4 through which extends operating handle5, said operating handle being pivoted at B to the body portion. Theoperating handle is provided at its underside with a depending portion lcarrying a pivot 8 on which is mounted a slotted member 9 forming oneleg of a toggle. The operating member is cut away adjacent to thedepending por- I2 of the leg 9 isin sliding engagement when the handleis moved toward the on position. The member 9 is pivoted at I3 to thelower leg I4 of the toggle and a coil spring I5 is provided normallybiasing the legs of the toggle toward "made position. The lower leg I4of the toggle comprises parallel arms I6 and I1 (Figure 6) rigidlyjoined'together and pivoted intermediate their ends, as at I8, to theupstanding sides I9 and I9 of a member 20 and provided at the ends,removed from the knee of the toggle, with a pivcted counter-weight 2I.The member 20 also comprises a base portion 22 rigidly connected as by astud 23 to a contact 24 and one end of a ilexible contact arm 25. Theother end of the contact arm 25 is rigidly secured, as by a stud 25, toa conducting member 21.

A stationary contact member 28 is secured to the body portion of thecircuit breaker as by a stud 29 which extends into a conducting sleeveto which is bolted a conductor lug 30 in a manner similar to that to behereinafter described in Figure 4.

From the underside of the top of the body portion I extends a plate-likemember 3l having a slot 54 therein into which the contact member 24extends in its off position.

The base portion 22 of the member 20 at its end remote from the stud 23is curved away from the contact arm on a wide radius so as to engage arelatively large area of said arm when the contacts are in engagedposition, thus avoiding a localized point of strain on the contact arm.

Upon either side of the contact member 28 are closely disposed plates 32and 32 of insulating material, one form of which may be composed ofasbestos bre bonded with magnesite cement. These plates are notched asat 33 to enclose the side edges of the contact 28 so as to lie closelyadjacent to the path of movement of contact 24. Located within the slot33 and resting on the contact surface of the contact 28 is a U-shapedmagnetic member 34 the legs of which extend wholly within the slots 33upon either side of the path of movement of the contact 24. At spacedintervals along the path of movement of contact 24 slots 35 and 36 areprovided ,in each of the plates 32, 32' and in these slots are imbeddedmagnetic members 31 and 38 in a similar manner to that shown at 34.These magnetic members are in a plane substantially parallel to theplane of the Contact member 24 when it is adjacent their position. Thenumber of these magnetic members 34, 31 and 38 will vary with the sizeand rating of the device and any of them may be omitted although it ispreferred that they appear in the general location as shown. In the endwall of the body portion I adjacent the arc suppressor vents 39 areprovided.

To the conducting member 21 is attached one leg of a U-shaped bimetallicmember 40 as by a stud 4I. The other leg of member 40 is secured by astud 42 to a conducting sleeve 43 extending through the portion 44 ofthe body portion l and to the upper end of which a conductor lug 45 issecured by a stud 46.

{It is thus seen that current passes through the device from lug 45through sleeve 43 to one leg of the bimetallic member through this legand the other leg of the bimetallic member to the conducting element 21,thence through the ilexible contact arm 25, contact 24, contact 28 andstud 29 to lug 30 by means of a conducting sleeve arrangement such asthat shown at 43 in Figure 4.

To the free end of the bimetallic. element 4I) is attached a striker 41having a threaded shaft cooperating with a threaded hole in the member48 and maintained in adjusted position by the nut 48. The striker ismounted in 'such position that upon movement of the member 40 under theaction of a predetermined current value it will engage against the kneeof the toggle and break it to permit the contacts to be separated underthe action of the energy stored in the spring contact arm 25.

'I'he shunt for the bimetallic member comprises two arms 49 and 50attached to the ends o! the legs of the bimetallicmember 40 by means ofthe studs 4I and 42 aforesaid. A These arms are separated from eachother and are adapted to be electrically connected at their free ends bythe U-shaped link 5I having its legs secured to the arms 49 and 50 bymeans of studs 52. The side of the body portion I is provided with anopening 53 which permits access to the link 5I so that it may be changedfor a different link having different resistance. The arms 49 and 50 ofthe shunt are formed with a predetermined resistance so that regardlessof the low resistance of the bridging link 5| the breaker will stillrespond to a desired predetermined value of current. Thus if a largecopper link were secured to the arms 49 and 5I), the resistance of theshunt would still be such that the current flowing through thebimetallic member 40 would give the desired maximum rating for thebreaker. With any greater resistance link across the arms it can readilybe seen that a greater proportion of the current will pass through thebimetal 40 and hence the breaker will operate at lower current values. Aselection of links 5I of predetermined resistivity alfords a desirablevariation in the rating of the breaker without changing the bimetal 40and without breaking the seal in the breaker enclosure. It can readilybe seen that a shunt arranged in this fashion has desirable safetyfeatures since under the worst possible conditions when a connectinglink of practically no resistance connects the arms 49 and 50 thebreaker will still operate at a safe current value due to the resistanceof the arms 49 and 50.

When a shunt link is connected across the arms 49, 50 there will be heatgenerated in the shunt by the passage of current therethrough which willaffect the member 40 through radiation. The movement of member 4l) willthen be due to a resultant of the heat generated therein by its owncurrent and that radiated from the shunt.

From the position of the parts in Figure 1 it can readily be seen thatthe initial movement of the operating handle counter-clock-wise to- Wardon position causes a force to be directed through the toggle legs 9 andI4 and member 20 upon the contact arm 25 above its eifective center ofrotation, thus tending to move the contact 24 upward away from thestationary contact 28. The contact 24 is, however, restrained frommovement by the upper surface of the groove 54 whereupon the contact arm25 is ilexed until the line of force through the toggle comes below theeffective center of rotation of said arm whereupon the energy stored inthe spring arm 25 by its flexure is expended by snapping contact 24 intoengagement with the contact 28 as shown in Figure 2, thus providing aquick make".

When the contacts are to be manually tripped to ff" position theoperating handle 5 is moved in a clock-wise direction whereupon the link9 through its frictional engagement at |2 with the curved surface of theoperating handle is rotated in a clock-wise direction about the pivot 0,thus breaking the knee of the toggle at the pivot I3 whereupon thecontact 24 quickly moves to its off position under the action of thespring contact arm 25, thus providing a quick break. Under the action ofthe spring I5 the toggle arms 9 and i4 will thereafter be straightenedout into made position as shown in Figure 1.

'I'he action of the automatic trip on over-load is shown in Figure 3.Here the bimetallic thermostatic member 40 has become heated due to anover-load current and has moved in a counterclock-wise direction so thatthe striker 4`| has engaged the knee of the toggle and moved it past itscenter or made position so that it will then collapse under the force ofthe spring contact arm 25 and separate the contacts. It is noted thatthis trip is entirely independent of the operating handle, thusproviding for trip free of the handle operation.

The theory of operation of the magnetic members 34, 31 and 33 is thoughtto be a drawing of the arc toward their closed ends and a forcing of itinto an elongated path curving in and out around the closed ends ofthese members, thus greatly elongating the path of the arc between thecontact members in their separated position. In conjunction with thiselongation the suppressor plates 32 and 32 are mounted closely adjacentthe path of movement of the movable contact 24 and hence operate toconfine the arc and provide cooling surfaces to aid in quickly quenchingthe arc. It is noted that the magnetic member 34 rests directly on thecontact member 20. It, therefore, exerts its effect on the arc at thevery moment of inception of the arc. The suppressor of which oneembodiment is shown in connection with the circuit breaker illustratedin Figures 1 to 'I inclusive, is highly efllcient in operation for allcurrent values and produces a result not obtainable for either theplates or the magnetic members alone. The stacked magnetic plates bythemselves work fairly well with high or short-circuit current values,however, these currents are not the only ones which the breaker isrequired to interrupt, but in its ordinary functioning will also operateto interrupt normal and subnormal current values and it is at thesevalues that the plates 32 and 32 are peculiarly effective since at thesevalues thc magnetic effect of the stacked plates has only a. smalleffect upon the path of the arc and does not serve to appreciablyelongate it. This is believed to be a disadvantageous feature of thestacked magnetic plate type of arc suppressor as while it functionsfairly well with very high current values, it is not designed for andwill not satisfactorily interrupt the normal and underload currentvalues. The plates 32 and 32' will of themselves function withacceptable elciency for the lower current values as they here confinethe arc and act to cool the arc stream. However, at the very high orshort-circuit current values the plates 32 and 32 alone will notfunction to quench the arc with sufcient rapidity due to the fact thatthey do not operate to elongate the path of the arc. The forrm ofsuppressor illustrated as a part of the breaker of Figures y1 to '7inclusive operates with greater efliciency at shorter time intervals atevery'current value than either the stacked magnetic plates or theinsulating suppressor plates taken alone and hence operates with a higheillciency over theentire range of currents to be interrupted fromsub-normal to short-circuit currents.

While the arc suppressor as herein illustrated may be used with any typeof circuit interrupting device it is peculiarly well suited for use withcircuit breakers having thermostatic over-load tripping devices as itconsiderably lessens the danger of burning out the thermostatic currentresponsive element. Heretofore the period running from the inception ofan over-load to the final interruption of the current has been dividedinto three roughly equal periods; the first being taken up in theself-heating of the thermostatic element by the over-load current; thesecond period being taken by the operating mechanism before the contacttips separate; and the third period being the duration of the arc beforeit is quenched. As the over-load current is flowing during all three ofthese periods, there has been considerable danger of burning out thethermostatic element and it has been necessary to use a relativelyheavier element to guard against destruction. By using the suppressorherein illustrated the time of the third period is very greatly reduced,thus providing either a greater safety factor in the same sized currentresponsive thermostatic element or permitting the use of a lighterthermostatic element with the same safety factor.

In Figures 8 to 11 inclusive a modied form of circuit breaker is shown.Parts similar to those illustrated in the breaker of Figures 1 to 'linclusive are here given the same numerals in the one hundred series.The breaker as herein shown embodies a base |03 having a cover |0| whichis scalable thereto to prevent unauthorized access to the breakermechanism. In the top of the cover |0| is a slot |04 through whichextends an operating handle |05. At opposite ends of cover |0| areprovided slots |39 and |53. Slot |53 is sealed off by means of a slidingcover |60 received in grooves in the sides of slot |53. Slot |39 ispartially sealed by an insulating plate |0| forming a part of the arcsuppressor structure. To the base |03 is bolted a U-shaped bracket |02.Between the arms of said bracket at its upper end the operating handle|05 is pivoted as at |06. 'I'he arms of the bracket |62 extend slightlybeyond the sides of the operating handle |05 and are received withinguides |63 and |63' forming between them guiding grooves on oppositesides of cover |0|. This arrangement prevents removal cf the coverexcept in a direction at right angles to the plane of the base |03. Thehandle |05 is provided with a depending lug |01 at one side thereto of athickness less than that of the handle member. On opposite sides of lug|01 are pivoted at |00 parallel arms |09 and |09 rigidly connected bytransverse web |09 and forming an upper leg of a toggle. The arm's|09`and |09' are pivoted at their lower ends at ||3 to parallel arms ||4and ||4 rigidly connected by transverse web I4 and forming the lower legof the toggle. A coil spring ||5 wrapped around the pivot ||3 has itsends engaging the transverse webs |09" and H4, thus biasing the legs ofthe toggle to their made position. At their lower ends arms ||4 and ||4'are pivoted to the upstanding sides ||9 and ||9 of member |20. Member|20 is provided below the sides ||9 and H9 with a curved portionengaging a flexible contact arm |25 in the same manner as in the breakerdisclosed in Figures 1 to 7 inclusive. The opposite end of member |20 isprovided with depending anges |64 which are pivoted at |65 to the upperendsv of parallel arms |66 and |66'. The lower ends of arms |66 and |66are pivoted at |61 to a member |68. Mounted on the upper face of base|03 is a conducting member |69; An extension of contact arm |25 extendsaround the curved end portion |10 of member |68 and is secured betweenconductor |69 and member |68 by means of studs |1| and |12. The oppositeend of contact arm 25 extends between the arms |66 and |66' and isrestrained in position between pivot |65 and the lower face of member|20. To this end of the contact arm a contact |24 is attached by meansof a rivet or other securing means.

One leg of a U-shaped bimetallic member |40 is attached to conductor |89by a bolt and nut connection |13. The other leg of said U-shapedbimetallic member is attached by means of a bolt and nut arrangement |14to a conductor |15 which extends through a double bend beneath thesliding cover |60 to the outside of the circuit breaker where it may beattached by means of 'bolt |16 to a lug or other conductor attachingmeans.

A member |11 formed generally in the shape of two spaced parallelinverted T-shaped portions |18 has webs 19 and |80 extending between theends of the cross arm of the T. The web |19 is slanted at an acute angleto the arm of the T. 'I'his web 19 may be formed as a solid connectionbetween the portions |18 but is illustrated as being separated, thisbeing a form which may be constructed more easily than the solid web.The vertical legs |8| of the double T-shaped member are located withinthe arms of the bracket |62 and are rotatedly mounted upon the pivot|06. Two small coil springs |82 and |82' urge the member |11 to rotatein a counter-clock-wise dircction. The member 11 is held againstrotation by means of an adjustable extension |83 held within the slot inthe bimetallic member |40. In its released position member |11 bearsagainst lug |84 extending from the lower face of the top of the cover|0| as shown ln dotted lines in Figure 9. vA stationary contact member|28 is secured to base |03 by means of a stud |85 and extends beneaththe back suppressor plate |6| to the outside of the circuit breakerWhere it may be attached by means of bolt |86 to a lug or otherconductor securing means.

Clearance is provided between arms |66 and the arms of the bracket 62and also between the member |18 and the legs of the toggle forinsulating purposes to prevent a shunting of the current about one legof the bimetal. 'I'he handle member is formed of insulating material andthis arrangement secures the desired insulation of the operating part.However, if desired, thin insulating sheets may be secured between arms|66 and the upright legs of bracket |62 and also between the members |18and the legs of the toggle to more surely insulate the operating partsand prevent a current path therethrough.

With the breaker in on position as shown in Figure 9, if the cover isremoved in the manner shown in dotted lines at top of said figure theguides |63 and |63' permit movement only at right angles to the base,this causing sufcient movement of handle |05 against the edge of itsslot to cause the knee of the toggle to engage the under surface of web|19, thus breaking the toggle and causing the operating mechanism toassume its "oiP position as in Figure 8 circuit breaker is in on"position.' With the cover removed it is impossible to operate thebreaker into on" position by means of the operating handle since theAinitial movement thereto causes actual upward movement of the contact|24, this contact no longer being restrained from such movement by plate|3I. This movement of the Contact causes such a change in the eiTectivecenter of rotation of the contact arm |25 that the line of force throughthe toggle always remains above such center of rotation and hence thecontact will not snap into engaged position. The upward movement of thecontact occurs about the pivot |65, the arms |66 being held from furtherupward movement by the positive engagement of their other ends with thecontact plate |69 and the contact arm |25 being restrained from upwardmovement relative thereto by the under surface of member |20.

The suppressor shown in this circuit breaker is very similar to thatdisclosed in the circuit breaker illustrated in Figures 1 to 7 inclusivewith the exception of the back plate 6| which extends across between theside plates |32. These side plates are, however, shown as being of alesser height and having extensions |81 of a length conforming to theunder face of the top of the cover member |0| for securing purposes.

The operation of the circuit breaker shown in Figures 8 to 10 inclusiveis as follows:

With the parts in the position shown in Figure 8 the breaker is innormal "off position. Rotation of handle member |05 in acounter-clockwise direction causes a force to be exerted upon theflexible contact arm |25 in a line above its effective center ofrotation. This tends to raise the contact |24 still further away fromcontact |28. A plate member |3| extending from the under side of the topof the cover 0| restrains the contact from further upward movement,hence the contact arm |25 is exed until the line of force through thetoggle comes below the effective center of rotation of arm |25 whereuponthe contact |24 is snapped into engagement with contact 28, thussecuring a quick make in the same manner as in the breaker of Figures lto 7 inclusive. In this movement due to the liexure of arm |25 the kneeof the toggle slips past the web 19 without contacting therewith. Theparts then assume the position shown in full lines in Figure 9. When itis desired to manually open the circuit breaker the handle 05 is rotatedin clock-wise direction from the position shown in Figure 9 whereuponthe toggle moves upwardly and to the left until the knee strikes theunder surface of web |19 whereupon the toggle linkage is broken andcontact |24 is quickly separated from contact |28 under the force of theenergy stored in the spring contact arm |25.

The automatic operation of the circuit breaker is as follows:

When an over-load current flows through the bimetallic element |40, thiselement becomes heated and bends to the right as shown in dotted linesin Figure 9 releasing extension |83 and permitting member |11 to rotatein a counterclock-wise direction under the action of the springs |82 and|82. Due to this rotation the under surface of web |19 strikes the kneeof the toggle and breaks the linkage so that contact 24 quicklyseparates from contact |28 regardless of the position of the operatinghandle. Extension |83 is adjustably carried on web |80 to permitadjustment of the amount of movement of the bimetallic member |40necessary to release the tripping member |11. When the device has beenautomatically tripped by an overload into position shown in dotted linesin Figure 9, it is re-set by turning the operating handle to its extremeright-hand positionvwhereupon the handle will positively engage the legs|8| ofA the member |11 and positively rotate it in a clock-wisedirection as shown, whereupon the extension |83 will slide down theinclined plane of the upper end of the bimetallic member |40 and againengage with the under surface of the slot therein. It should, of course,be obvious that a shunt 49 similar to that disclosed in Figures 1 toinclusive may also be used across the legs of the bimetallic member |40to function in a similar manner.

In Figures 12 and 13 aslightly modiiled form of arc suppressor is shown.Herein the side walls |81 and |81 and end wall |88 are formed as aunitary molded piece. Slots |89 are provided extending from the frontends of the sidewalls |81 and |81' and within these slots are arrangedthe U-shaped magnetic members |90. A stationary contact arm |9| hasmounted directly upon its upper face a contact |92. Surrounding thiscontact |92- on three sides is a U-shaped magnetic member |93. 'I'hesuppressor structure in this form rests upon the Contact arm |9|, theside plates |81 and |81 of the suppressor being cut out as at |94 toprovide clearance for the contact and magnetic member I 93. The upperportions of side walls |81 and |81 are cut out on their inner faces asshown at |95 to provide additional clearance for contact blade |96 toguard against leakage of current through said side walls. The movablecontact |96 in this form is shown as a straight bar having areciprocatory movement.

In Figure 14 another modified form of arc suppressor is shown similar tothat shown in Figures 12 and 13 except that the side walls |91 and backplate |98 are here separately formed and are joined together in positionupon the stationary contact arm, The slots |89 in side walls |91 do notin this arrangement extend to the front edge of the side walls but arecontiguous in length with the side faces of the magnetic members.

It is obvious that many other variations may be made in the form of thearc suppressor, it being only necessary to provide in some mannerparallel insulating faces closely adjacent to the path of the movableContact and having U-shaped magnetic members with the inner faces of thelegs thereof also closely adjacent to the path of the movable contact.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the inventionl is notlimited thereto as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims,

What s claimed is:

1. In a circuit controlling device, a stationary contact, a movablecontact, a ilexible contact arm carrying said movable contact andnormally biasing it to open circuit position, an operating handle, atoggle linkage inter-connecting said handle and said arm, the line offorce through said toggle upon initial movement of said handle beingdirected above the effective center of rotation of said arm thus tendingto further separate said contacts.

2. In a circuit controlling device, fixed and movable contacts, flexiblemeans carrying said movable contact and normally urging it toward openposition, iixed means limiting the open movement of said movablecontact, and means for actuating said movable contact, operating bymovement in a single direction to initially urge said contact towardfurther separated position and flex said first mentioned means, theilexure of said means then snapping said contact into closed circuitposition.

3. In a circuit controlling device, relatively movable contacts, ailexible contact arm for one of said contacts stressed to urge it towardopen position, an operating handle and a toggle linkage between saidoperating handle and said flexible arm for engaging the contacts, theline of force through said toggle moving from above to below theeffective center of rotation of said arm upon movement of the operatinghandle to produce a quick make.

4. In a circuit controlling device, a stationary contact, a movablecontact, a flexible contact arm ,carrying said movable contact andnormally biasing it to open circuit position, an operating handle, atoggle linkage interconnecting said handle and said arm, the line offorce through said toggle upon initial movement of said handle beingdirected above the effective center of rotation of said arm and tendingto further separate said contacts, means restraining said movablecontact from actual further movement and causing ilexure of the contactarm until the line of force through the toggle passes below theeffective center of rotation of said arm, whereupon the movable contactis snapped into closed circuit position.

5. In a circuit controlling device, a stationary contact, a flexiblecontact arm carrying a movable contact at one end, the opposite end ofsaid arm being fixed, said arm normally biasing the movable contacttoward separated position, means to actuate said arm to snap saidcontacts into engagement with quick make, said actuating means holdingthe contacts engaged, the release of said actuating means permittingquick separation of the contacts under the bias of said arm.

6. In a circuit breaker, a stationary contact, a flexible contact armcarrying a movable contact at one end, the opposite end of said armbeing fixed, said arm normally biasing the movable contact towardseparated position, means to actuate said arm to snap the contacts intoengagement with a quick make, said actuating means holding the contactsengaged, the release of said actuating means permitting separation underthe bias of said arm, means for manually releasing said actuating meansand means for automatically releasing said actuating means in responseto an over-load.

'7. In a circuit breaker, a stationary contact, a Contact arm carrying amovable contact at one end and means including a togglefor actuatingsaid contact arm, a normally stationary pivoted member having a strikerportion thereon, the knee of the toggle passing said portion withoutcontact when moving toward on position, the knee of said toggle engagingsaid portion when the actuating mechanism is initially manually movedtoward oil position to break the toggle and insure a quick break, andmeans for automatically moving said member and striker portion inresponse to an overload to break the toggle.

8. In an automatic electric circuit breaker, a stationary contact, anoperating unit comprising a movable contact, a contact supporting armand mechanism for moving said arm to open and ciose the circuit throughthe breaker and a cover for said breaker carrying a part adapted toengage a movable part in said unit to provide for closing oi' thecircuit through the breaker, rernoval of said cover and the part carriedthereby rendering said mechanism ineffective to move said arm to closethe circuit. i

9. In an automatic electric circuit breaker, a base, relatively movablecontacts mounted on said base, manually operable mechanism for openingand closing said contacts carried by said base, current responsive meansfor automatically opening said contacts carried by said base, a covermounted over said parts and secured to the base, and means preventingoperation of said mechanism to close the contacts when the cover isremoved.

10. In a circuit controlling device, a base, a stationary contact, amovable contact, operating mechanism for said movable contact, aremovable cover cooperable with said base to seal the breaker, saidoperating mechanism being inoperable to close the contacts unless theopening movement of the movable contact be limited and means on saidcover for limiting movement of said movable contact whereby themechanism cannot be operated to close the contacts when the cover isremoved.

11. In a circuit breaker, a base, a stationary contact mounted on saidbase, a movable contact, a iiexible contact arm mounted on said basecarrying said movable contact at one end, operating mechanism for saidmovable contact, a manually operable handle actuating said mechanism,spaced arms mounted on said base supporting said mechanism and handle, aremovable cover cooperable with said base to seal thebreaker, guides onsaid cover receiving said arms to provide for longitudinal movement ofsaid cover, the handle being interlocked with the cover to prevent suchmovement of the 'cover while the contacts are engaged.

12. In a circuit breaker, automatic means for tripping said breakerincluding a series connected thermostatic member, and a shunt for saidmember comprising separated arms of predetermined resistance and aninterchangeable link bridging said arms, the resistance of said armsbeing such that with a link of no appreciable resistance the shunt willnot'by-pass more than a predetermined portion of the circuit current.

13. In a circuit controlling device, stationary and movable contacts, acontact arm carrying said movable contact and biased to separatedposition, an operating handle, a toggle interconnecting said handle andarm, said toggle having a frictional engagement with said handle,whereby initial movement of the handle toward off position Will breakthe toggle to cause snap actuation of the Contact arm under the actionof said bias.

14. In a circuit controlling device, stationary and movable contacts, acontact arm carrying said movable contact and biased to separatedposition, an operating handle, a toggle having one leg connected tothecontact arm and its other leg having a pin and slot connection withthe handle, and an abutment on the handle slidably engaging said otherleg, whereby upon initial movement of the handle toward oiT' positionthe friction of said slidable engagement Will break the toggle to causesnap actuation of the contact arm under the action of said bias.

15. In an automatic electric circuit breaker, separable contacts, meansfor effecting automatic separation of said contacts including currentresponsive means, and a shunt for said current responsive meanscomprising xed and variable portions, the resistance of the xed portionsbeing such that when the resistance of the variable portion isnegligible the shunt will not by-pass more than a predetermined portionof the circuit current. n A

16. In an automatic electric circuit breaker, separable contacts, meansfor automatically separating said contacts including a series connectedbimetallic member, and a shunt for said member comprising fixed andvariable portions, the resistance of the fixed portion being such thatwhen the resistance of the variable portion is negligible the shunt willnotby-pass more than a predetermined portion of the circuit current.

17. In an automatic electric circuit breaker, a scalable enclosure,separable contacts and means for automatically separating said contactswithin said enclosure, said means including a series connectedbimetallic member, and an adjustable shunt for said member accessiblefrom the eX- terior of the enclosure without `disturbing said seal.

18. In an automatic electric circuit breaker, a scalable enclosure,separable contacts and means for automatically separating said contactswithin said enclosure, said means including a series connectedbimetallic member, shunt terminals for said member accessible from theexterior of the enclosure, and interchangeable links of predeterminedresistance connectable across said terminals to by-pass a portion of thecircuit current around said member.

19. In an automatic electric circuit breaker, separable contacts, meansfor automatically separating said contacts including a series connectedthermostatic member, and a shunt for said member comprising an opencircuit xed portion having a predetermined resistance, andinterchangeable elements of predetermined resistance connectable toclose the shunt circuit and by-pass a portion of the circuit breakercurrent around said member, the resistance of the xed portion being suchthat with an element of negligible resistance the shunt will not by-passmore than a predetermined portion of the circuit current.

20. In an automatic electric circuit breaker, a scalable enclosure,separable contacts and means for Aautomatically separating said contactswithin the enclosure, said means including a series connected bimetallicmember, a partial shunt of predetermined resistance for said memberwithin the enclosure and having terminals accessible from the exteriorof the enclosure, and interchangeable links of predetermined resistanceconnectable across said terminals to complete the shunt circuit, theresistance of said partial shunt being such that a link of negligibleresistance the shunt will not by-pass more than a predetermined portionof the circuit current.

21. In an automatic electric circuit breaker, separable contacts,automatic means for separating said contacts including a seriesconnected U-shaped bimetallic member, spaced arms of predeterminedresistance connected to the legs of said member, and interchangeablelinks of predetermined resistance connectable across said arms tocomplete a shunt circuit for said member, the resistance of said armsbeing such that with a link of negligible resistance the shunt Will notby-pass more than a predetermined portion of the circuit current.

JOHN G. JACKSON.

